Develop granulocyte-macrophage and lymphocyte progenitors from transplanted marrow cells, utilizing agar cultures to monitor granulocyte macrophage and B-lymphocyte populations in spleen colonies and the various host organs following injection of marrow cells into irradiated recipients. Parallel studies shall be done involving transplanted marrow cells to a variety of non-irradiated recipients with genetic anomalies of hemopoiesis. Attempts shall be made to modify the proliferation of transplanted marrow cells in recipients by use of a variety of stimulating factors including injection of purified GM-CSF.